1. Field of the Invention
The invention generally relates to computer systems or computer-implemented systems employing translating or optimizing compilers and methods, and, more particularly, to dynamic translating compilers and methods.
2. Related Art
A variety of techniques are known for static translation of the executable instructions of a computer software program. Such known techniques are implemented by static compilers, i.e., compilers that translate a program prior to execution. One disadvantage of such techniques is that the dynamic behavior of a program typically is more readily and accurately ascertained while it is being executing than while it is being compiled prior to execution.
Some systems and methods exist that avoid this disadvantage by a process generally referred to as dynamic translation. That is, a dynamic compiler operates upon an executable image of the original software program as it is being executed at run time. Typically, the dynamic compiler is thus better able to deduce those paths that execution is most likely to take through particular portions of the program (often referred to as the control flow through the instructions of the program).
Such known dynamic translation systems may be designed to accomplish one or more of a number of tasks. One task is referred to as cross-platform translation, in which a program designed and written for execution on a computer system having a particular architecture and operating system is translated so that the translated program may be executed on another type of computer system. Some existing dynamic translation systems include "Daisy" by International Business Machine Corporation, "fx!32" from Digital Equipment Corporation, and "Wabi" from Sun Microsystems.
Dynamic translation systems are also used for instrumentation and profiling of programs without the need for recompilation. The term "instrumentation" refers generally to the insertion of special code to detect or record various parameters of execution, and "profiling" refers generally to reporting such parameters. Such use may also be referred to as "monitoring." Examples of existing products intended for such uses include "Shade" from Sun Microsystems and "ATOM" from Digital Equipment Corporation.
Such tasks of dynamic translation systems generally are also undertaken by static translation systems, albeit with the noted disadvantage. However, another task traditionally carried out by static translation systems is not adequately carried out by known dynamic translation systems. Such task is optimization; that is, the alteration, deletion, rearrangement, or other revision of instructions, or the addition of new instructions, with the specific objectives of increasing the speed of execution of executable instructions, decreasing the amount of computer resources needed for such execution, or both. Therefore, what is needed is a system and method for increasing the opportunities for dynamic optimization of executable instructions.
In particular, what is needed is a system and method for determining those particular sequences of instructions of an original executable file such that, if the instructions are translated and optimized, quicker execution, reduced resource usage, or both, will most likely be achieved. Such selectivity generally is advantageous because it is possible to spend more time translating and optimizing instructions than will be gained by such translation and optimization. For example, control may flow through a group of instructions that, for any of a variety of reasons, is not amenable to, or significantly benefited by, optimization. Accordingly, what is particularly needed is a system and method for selecting sequences of instructions, based on control flow through such instructions at run time, that are most amenable to dynamic optimization.